Adapting apparatus for fluorescent lamps



July 7, 1959 F. KNOBEL 2,894,232

ADAPTING APPARATUS FOR FLUORESCENT LAMPS Filed May 24, 1954 2 Sheets-Sheet 1 INVENTOR. fizz/ #019 a) fl l 2 Sheets-Sheet 2 F. KNOBEL ADAPTING APPARATUS FOR FLUORESCENT LAMPS FIG .8

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ADAPTING APPARATUS FOR FLUORESCENT LAMPS Fritz Knobel, Ennenda, Switzerland Application May 24, 1954, Serial No. 431,986 Claims priority, application Switzerland May 27, 1953 1 Claim. (Cl. 33690) The inveniton relates to an adapting apparatus for the operation of tubular fluorescent lamps.

In adapting apparatus for such lamps, very great importance is generally given to the provision of large longitudinal extension and having little or no humming.

These two conditions are opposed to each other in so far as an apparatus sufficiently free of hum must have no exteriorly apparent magnetic stray field, which can best be achieved with a near-cubic form of the adapting apparatus. If for the magnet core, present in all adapting apparatus, a certain slimness or fineness ratio, length: cross section is exceeded, the magnetic stray field becomes excessively efiective and causes vibrations by influencing the laminated core plates and adjacent metallic parts, which themselves produce strongly disturbing humming noises. in known adapting apparatus of slim or oblong execution, hum is avoided by using instead of one single magnet core with coil, several shorter cores with partial coils, which are connected with each other and are cast into a sheet iron casing consisting of bonnet or hood and bottom by means of resinous compound. This execution has the disadvantage of being very complicated and costly. In addition, the use of partial coils results in a greater core weight and also in greater magnet losses, at the same effective coil length.

In further known construction the active parts consisting of magnet cores and coils are pressed into fittings made of profiled aluminium tubes. This type of construction may well be suitable for the manufacture of complete illumination fittings having a given uniform shape; they are however, unsuitable for adapting apparatus, which are to be built into all sorts of fittings or, which as it is often the case, must be mounted separately. In addition a profiled tube made of aluminium would not be very suitable for such adapting apparatus since the magnetic stray field will not be screened, so that if used in a sheet iron fitting the latter would produce heavy humming noises. Experience has also shown that such fittings are still not satisfactory with respect to humming and that the discharge of the lamp may be influenced by the relatively strong magnetic stray field through the aluminium tube and may cause disturbing spiral flow.

It is therefore an object of the invention to provide an adapting apparatus having a casing made of a steel tube of conventional construction, the profile of this tube being such that a magnet core carrying the coil is fixed at its sides. Such an adapting apparatus is mainly suitable as an accessory part for a fitting for fluorescent lamps, which fittings are made in the usual manner of sheet metal. The sheet metal fitting contains further the remaining accessories as, starter condenser and sockets in as far as these parts are not mounted in the adapting apparatus according to the invention.

In the wall of the steel tube two channels are arranged opposite each other, which serve to fix the magnet core, and between these two channels the walls of the tube are bent outwards to provide space for the coil winding. At

nited States Patent Patented July 7, 1959 least on the one face side of the steel tube terminals are arranged.

The steel tube can be filled out with cast-in artificial resin. Thereby the parts arranged in the tube i.e. choke condenser, transformer, can be protected against moisture and humming can effectively be prevented.

In very complicated adapting apparatus, where several parts have to be arranged in the profiled tube, the use of tubes made of one piece may prove to be a disadvantage, since the different parts must be slid in from one face side in fully wired condition so that a checking of the assembly by eye or a correction can no longer be made. Also in certain countries drawn profile tubes are difficult toobtain. In such cases the profile tube can be made of two parts, so that the two halves are provided with projections and recesses, which can be brought into engagement so that these halves will provide a tube of great strength in assembled state.

A further measure to obtain an adapting apparatus having the least possible humming noise, is to fill the air gap of the magnetic core with a compound of artificial resin in order to glue the arms of the core plates together. The invention also relates to an improved process for the production of such an electric choke free of humming, the magnet core having an air gap as provided in the adapting apparatus according to the invention. To this end a compound of artificial resin is filled into the coil sleeve of the upright coil containing one half of the magnetic core whereupon the other half of the magnetic core is pressed into the coilsleeve, so that the resinous compound will flow into all the gaps between the core plates and between core and coil sleeve and after the heat treatment of the compound, will bind these two parts together to one solid body. The construction of the magnetic core for the apparatus according to the invention is equally of importance.

Above all the air gap, which usually is necessary for chokes, must only be provided in the inner core arm. According to the invention this is achieved by providing a magnetic core, consisting of two symmetrical E-shaped core halves, their inner arms which project into the coil, being shortened each by one half of the Width of the air gap. When the core halves are pressed into the coil, the outer arms will come into contact with each other, while the inner or middle arm will form the necessary air gap. In order to stamp these E-shaped core plates with the smallest possible amount of punchings, i.e. waste of material it is necessary to make the outer arms of equal width as the windows. If the punch is shaped accordingly it is then possible to stamp the arm of the one core plate from the window of the adjacent plate. This results in substantially smaller losses of material as compared with the conventional manner of stamping.

With these and other objects in view, the invention includes certain novel features of construction and methods, the essential elements of which are set forth in the appended claim and preferred embodiments, which are hereinafter described with reference to the drawings, which accompany and form a part of the specification.

In said drawings:

Fig. 1 is a cross section of a profiled tube,

Fig. 2 shows a longitudinal section through an adapting apparatus,

Fig. 3 is a front view according to Fig. 2,

Fig. 4 is a side View of a casing according to a second embodiment,

Fig. 5 is a cross section along line V-V in Fig. 4 showing a choke inserted in the casing in front view,

Figs. 6 and 7 are fragmentary side views of modifications with respect to Fig. 4,

Fig. 8 is a longitudinal section of a coil with magnetic core,

Fig. 9 is a plan view according to Fig. 8,

Figs. 10-16 show the method of production of E- shaped core plates for chokes in adapting apparatus.

The profile tube 1 shown in Fig. 1 having uniform wall thickness, is folded from sheet steel, welded and drawn to dimension. It concerns so-called welded cold drawn steel tube, obtainable on the market. It can however, be made of two single pieces, which are welded together as shown in Fig. 1. The tube has two channels 2 arranged opposite each other. Between these channels bent walls 3 are provided. The channels 2 are adapted to hold the magnet core 4 of a choke by clamping the core between the channels. The bent walls provide a free space in which the coil 5 of the choke is arranged. The exterior dimensions of the profile are approximately 1.7 X 1.5. Instead of a choke a transformer can be arranged in the tube in the same manner. If necessary also a condenser can be provided in the tube. A steel plate 6 is welded to one face side of the tube, the plate holding a terminal '7. The other face side can also be provided with such a terminal. 8 and 9 designate two screw bores for the attachment of the adapting apparatus.

The profile tube is advantageously filled by a cast-in artificial resin or a suitable compound of such material. This filling is made after choke, transformer and/or condenser are inserted, in order to avoid humming and to protect the inserted parts from moisture.

In the embodiment according to Figs. 4 and 5 the casing of the adapting apparatus is sectioned in one longitudinal middle plane into two equal parts 10 and 11 forming together the profile tube. Each of the two parts is provided on one side at the dividing edge with two dovetailed projections 12 and on the other side with two corresponding recesses 13. These projections 12 and recesses 13 are provided in such a manner, that the projection 12 can be brought into engagement with the recesses 13 by transversally moving the two parts with respect to each other. A profile tube constituted in this manner has again two channels arranged opposite each other, into which the magnet core can be inserted. The profile of the tube is such, that the coil of the choke will have sufiicient space. After the magnet core is inserted the latter prevents an axial displacement of the two parts 10 and 11 so that they are secured in their engaging position.

Instead of dovetailed projections 12 and recesses 13 or notches, also T-shaped projections 1.6 and notches 17, or circular projections 18 and notches 19 can be provided as shown in Figs. 6 and 7 respectively.

Instead of only two projections and notches, a larger number of said portions can be provided.

In the embodiment according to Figs. 4 and 5, the two parts it) and 11 may be made of magnetic material.

Instead of being made of two equal parts, divided in its middle plane as shown in Figs. 4-7, the casing of the adapting apparatus can also be made of one U-shaped member and a bottom plate being provided with ribs, which slidably engage longitudinal notches as shown in Fig. 19. The ribs and notches can be of T-shaped, dovetailed or circular cross-section.

The casing 20 of the coil shown in Figs. 8 and 9 is suitably made of a steel tube of uniform wall thickness. Into this tube 20 the magnet core made of two halves 21 and Z2 is inserted, its outer parts being held in a channel portion 23 of the tube 20 and clamped fast by depressions 24 in the tube. The air gap between the two core halves is filled with a composition of artificial resin. The magnet core is partially enclosed by a hard-paper sleeve 26 around which the coil is wound.

In fabrication of the choke, the sleeve 26 with its coil 27 is pushed over one half of the magnet core 21. Then the choke is placed vertically on a base e.g. a working table, with the free opening of the sleeve upwardly and the core half 21 downwardly directed. Into the sleeve a certain amount of artificial resin composition is now cast, so that upon insertion and pressing home of the second core half 22, the air gap is completely filled by the artificial resin composition 25 and that in addition an excess quantity of this composition 25 will be pressed into all gaps between the plates of the core and between sleeve and core. In this manner, the interior part of the magnet core, which is arranged in the sleeve, will become a solid body after the heat treatment for hardening or thermo setting of the composition 25. Vibrations of the core plates are thus made imposible.

The choke is then inserted into a profile tube 241, serving as casing, which has a groove to receive the exterior parts of the magnet core. Since it is not very well possible, to adjust the height of the core consisting of plates of 0.51 mm. thickness, so that the core will be sufiiciently pressed and held by the groove, the profile tube with inserted choke is placed in a press in which depressions 24 in the tube 20 are produced (Fig. 9). Thus the magnetic core is pressed together in the interior of the profile tube, thus preventing vibrations of the core in the tube.

The chokes or transformers manufactured in this manner are subsequently impregnated with an insulating lacquer in a known manner.

Such chokes and transformers can be used in every application where it is of importance that the parts will be as noiseless as possible, e.g. for adapting apparatus for fluorescent lamps or as so-called blocking or suppression chokes.

For transformer cores, it is usual to place in one plate layer a plate with short arms and one with long arms each, as shown in Fig. 10. In this case the assembly is made in such a manner that alternatively a long plate is placed over a short plate, whereby the joint 33 is covered. The size of the core plates having the same induction in their outer as in their middle arms, the ratio must be The dimension 0 however, can be varied in wide limits and is of no importance for the present case. For transformer cores it is usual, that two core halves 34 and 35 of the same size are arranged in the same plane opposite each other such that a gap 36, through going as shown in Fig. 11, is formed. This construction has the disadvantage that an undesirable magnetic stray field is created which in the construction according to Fig. 12, where only the middle arm has an air gap is substantially reduced. This core consists of plates of equal E-shaped contour 37 and 38, their middle arms being shortened by one half of the width of the air gap. If the points fit correctly, practically no magnetic stray field will be present which would produce vibrations in the adjacent casing or fittings and the disturbing humming noises.

The stamping of the E-shaped plates is usually done in so-called complete cuts. It can however, also be done in follow-up cuts from bands or strips 40 according to Fig. 13, and 41 according to Fig. 14. The hatched parts 42 and 43 respectively will be cast as punchings or waste. In a cut 44 according to Fig. 15 having the following measurements a=15 mm., b=6.75 mm., d=6.8 mm. and e=55 mm., this loss of material is 52% of the weight of the E-shaped plate.

Since the material used for this purpose is relatively expensive, such a loss of material will considerably increase the manufacturing costs. According to the invention this loss of material is reduced to a minimum by stamping the outer arms of the plates from the windows of the adjacent plates. To make this possible it is naturally important that the width of the outer arms is the same as the one of the windows. The method according to the invention will be described with reference to Fig. 16.

As shown in this figure the E-shaped plates 44 (in Fig. 15) can be stamped from a sheet strip 45 in a follow-up cut, by means of accordingly shaped tools, so that the outer arms of the plates will coincide with the windows of the adjacent plates. The hatched surface again shows the losses, which for the plate according to 'Fig. 15 are only about 11% i.e. one fifth of the previous losses. In other cases where windows and outer arms of the plates are wider, the ratio is still better.

In the same manner E-shaped plates having shortened middle arms can be stamped. The stamp can hereby be provided with replaceable inserts, by means of which the middle arm of the plate can be varied.

What I claim is:

An adapting apparatus for fluorescent lamps comprising a casing formed by a single piece of profiled steel tube, the profile of said steel tube forming two channels disposed opposite each other, a magnetic core disposed Within said tube, said magnetic core being constructed of a plurality of magnetizable layers arranged to form a laminated assembly, the opposite ends of the laminate assembly being disposed in said channels, said laminate assembly having a dimension in the direction perpendicular to the plane of said layers which is substantially equal to the inside corresponding dimension of portions of the side walls of said channel so that said wall portions exert pressure on the laminate and urge the layers thereof into intimate contact, the walls of said tube being bent outwardly between the channels and receiving the winding of a coil on said core, said wall portions including depressions formed in the channel side walls, the inner surfaces of which engage the magnetic core and press the laminations thereof tightly together, an end plate having the shape of the profile of the steel tube closing one end of said tube, and a terminal formed on said end plate.

References Cited in the file of this patent UNITED STATES PATENTS 1,236,796 Wehmeier Aug. 14, 1917 1,702,159 Grunow Feb. 12, 1929 2,109,837 Davis Mar. 1, 1938 2,399,103 Clinedinst Apr. 23, 1946 2,441,213 Sutter May 11, 1948 2,572,590 Bjorklund Oct. 23, 1951 2,629,076 Lloyd et al -1 Feb. 17, 1953 2,682,644 DEsopo June 29, 1954 2,741,528 Clark et al. Apr. 10, 1956 FOREIGN PATENTS 339,832 Great Britain Dec. 18, 1930 

